The present invention pertains to a method for processing a spectacle lens comprising the steps of (1) measuring a lens and (2) processing the measured lens. The measuring step comprises obtaining optical information about the lens such as a prism value and other optical properties, as measured at a position of an optical reference point by using a lens meter. The subsequent processing step comprises processing the spectacle lens using the optical information obtained in the measuring step, wherein the optical information obtained is used as a portion of data for directing the processing of the lens. The present invention also encompasses a lens meter that includes an information processing portion for obtaining optical information used for directing the processing of the lens.
Typically, a spectacle glass, such as an eyeglass or monocle lens, is prepared by processing an uncut spectacle lens (in general, a so-called round lens having a circular shape) into a desired shape corresponding to fit the shape of a spectacle frame. Then, the properly cut lens is fitted into the spectacle frame. The uncut round lens is prepared and supplied by a lens manufacturer, who selects the proper lens based on the data of the prescription of the eye of the person who will be wearing the spectacle glass. Typically, the useful eyeglass prescription data includes dioptric power, cylindrical dioptric power, the distance between the right and left eyes of the eyeglass wearer, and other like data. Furthermore, the manufacturer needs to know data on the shape of the spectacle frame selected by the person who will be wearing the spectacle glass and additional layout information.
Relevant measurements of the round lens supplied by the lens manufacturer are conducted by the manufacturer using a lens meter. The position of the optical center and the cylinder axis of the lens are obtained and marks showing the position of the optical center and the angle of the cylinder angle are placed on the lens. The marks are used as guide marks to show the position and the angle of attachment for a lens holder that is to be attached to the uncut lens before the lens is processed. The lens holder serves as a jig to define the axis of rotation for the lens during processing.
According to the conventional method for determining the position of the optical center of an uncut lens, a lens meter is used to measure an optical property of the lens, such as the prism value, at a position (a xe2x80x9cpoint of measurementxe2x80x9d) on the lens empirically estimated to be close to the optical center. The measurement is repeated at different estimated positions (xe2x80x9cpoints of measurementxe2x80x9d), where each subsequent estimated position is determined by a reiterative computer algorithm, until a position is obtained where the difference between estimated positions is approximately zero. When this condition is found, the estimated position is taken to be the position of the true optical center. For an example of such a reiterative method, reference is made to the specifications of Japanese Utility Model No. 2569718 and Japanese Utility Model Application Laid-Open No. Heisei 1(1989)-135344).
In actual practice as shown in FIG. 14, a mark 600 is placed at the position of the optical center (O.C) of the spectacle lens, and two other marks 600a and 600b are placed at positions on either side of the optical center to define a straight line passing through the position of the optical center. This straight line is used to show, or define, the cylinder axis. Thus, the uncut lens has three marks.
However, it is a very complicated, tedious, and difficult task to visually measure the prism value or other optical properties at a position considered to be close, or approximate, to the true optical center. Specifically, it requires skill to use a lens meter to find a position on the lens where the value of the prism value is zero. Such a process requires a long time to determine an accurate position. Moreover, in the case of a plastic lens, sufficient care must be taken not to form scratches on the lens during this measuring process because the lens is moved on a processing table with each measurement.
The present invention has been conceived under the above circumstances, and has as an object, providing a method for processing a spectacle lens which enables convenient marking at a selected point of measurement on the lens. The marking is performed easily and rapidly without forming scratches on either the lens or the lens meter.
In accordance with the above aspects of the present invention, the data are saved representing the relative positions describing the relationship between the position of the mark placed at the selected point of measurement and the position of an optical reference point, which includes the position of the optical center. Therefore, when the position of the mark is detected to facilitate lens processing and the above relative positions are read, the position of the optical center or the like relative to the detected mark position can be known immediately. The position of blocking (also known as the xe2x80x9cposition of attachmentxe2x80x9d for the lens holder) can be decided based on the information obtained above and a lens holder can be attached so that the uncut lens can be properly processed by a lens cutting or grinding apparatus.
In accordance with one embodiment of the present invention, there is provided a method for processing a spectacle lens comprising the steps of: supplying an uncut lens and setting the lens in a lens meter; measuring optical properties of the lens at a point of measurement on the lens to generate measured data, wherein the optical properties include a prism value; calculating a calculated optical reference point position, including a calculated position of an optical center of the lens using the measured data; marking the lens with a mark placed at a position on the lens at the point of measurement or at a point relative to the point of measurement, and generating first mark data representing the position of the mark; processing the first mark data to determine a relative relationship between the position of the mark and the calculated position of the optical reference point, thereby generating third data representing the relationship between the position of the mark and the calculated position of the optical reference point; saving the third data to a memory medium, or recording the third data to a recording medium, or transmitting the third data from the lens meter to a lens processing apparatus, so that the first data is subsequently available for affecting lens processing; removing the lens from the lens meter and setting the lens on a processing table of a lens processing apparatus where blocking is performed; detecting the mark on the lens and measuring the position of the detected mark to generate second mark data, wherein the second mark data represents the position of the mark as measured; reading the third data from the memory when saved or from the recording medium when recorded, or receiving the third data from the lens meter; specifying a specified position of an optical reference point, including a specified position of the optical center, on the lens wherein the specified position of the optical reference point is determined using the measured mark data and the third data; blocking a lens holder to the lens at a position of attachment on the lens, where the position of attachment corresponds to the specified position of the optical reference point; and subsequently cut processing the uncut lens while blocked to the lens holder to produce a spectacle lens.
In accordance with another embodiment of the method of the present invention, it is sufficient during the step of measuring a lens that a mark be placed simply at a desired selected position. Complicated operations, such as measuring the prism value or the like at different positions on the lens with a lens meter to find the position where the specific optical property value obtained by the measurement becomes zero, are not necessary. Consequently, the guide mark can be placed rapidly and there is no possibility of forming scratches on the lens since the lens is not moved on the processing table during this marking process.
In accordance with another embodiment of the invention, the present invention is a lens meter comprising a first portion for measuring optical properties of an uncut lens; a second portion for marking the measured lens, and a third portion for information processing.
The method for processing a spectacle lens as well as the lens meter for measuring and marking the spectacle lens are described below as different embodiments of the present invention with reference to the Figures. Further objects, features and advantages of the present invention will become apparent from the Detailed Description of the Preferred Embodiments, which follows, when considered together with the attached drawings.